Isotones have

Options

A. same mass number but different atomic numbers
B. same atomic number but different mass numbers
C. same value of (mass number - atomic number)
D. same number of electrons

Explanation

**Step-by-Step Solution:**

1. **Understanding Isotones**: Isotones are defined as atoms that have the same number of neutrons but different numbers of protons (atomic numbers). This means that while the neutrons are the same, the atomic structure varies.

2. **Analyzing the Options**:
- **Option A**: "Same mass number but different atomic number." This is incorrect because isotones do not necessarily have the same mass number; they have the same number of neutrons.
- **Option B**: "Same atomic number but different mass number." This is also incorrect because isotones must have different atomic numbers.
- **Option C**: "Same value of mass number minus atomic number." This is correct because the number of neutrons can be calculated using the formula: Neutrons = Mass Number - Atomic Number. If isotones have the same number of neutrons, then this value must be the same.
- **Option D**: "Same number of electrons." This is incorrect because isotones can have different numbers of electrons depending on their atomic number.

3. **Conclusion**: The correct answer is that isotones have the same value of mass number minus atomic number, which corresponds to the number of neutrons.

**Final Answer**: Isotones have the same number of neutrons.

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